Method and apparatus for alternate destination routing for switching egress customers

Abstract

Redirection of calls from a busy primary destination to a secondary destination of a switched egress alternate destination redirection (ADR) customer is performed in the absence of sufficient terminating line status information in the form of either a busy or free indication being provided to the originating switch which provides the ADR service feature capability. The originating switch infers that the primary destination is busy and redirects the call to the secondary destination accordingly if the time that passes since the inception of the call is greater than a predetermined interval in which the call has not been answered.

We claim: 
     
       1. A method for redirecting a telephone call from a busy primary destination to a secondary destination of a switched egress alternative destination redirection (ADR) customer when either a busy or free indication is not provided, comprising the steps of: determining the primary and secondary destination subscribed to by the ADR customer;   providing signalling information to a local switch for routing the call to the primary destination;   starting a timer for timing a predetermined interval if the local switch does not provide either the busy or the free indication associated with the primary destination; and,   redirecting the call to the secondary destination if the timer times the predetermined interval before the call is disconnected or before the call is answered at the primary destination.   
     
     
       2. The method of claim 1, wherein one local network comprises the primary destination and the secondary destination. 
     
     
       3. The method of claim 2, further comprising the step of establishing a voice path from the calling party to the primary destination if the primary destination is determined to be free. 
     
     
       4. The method of claim 1, wherein the primary destination and the secondary destination are contained in a first and second local network, respectively. 
     
     
       5. The method of claim 4, further comprising the step of establishing a voice path from the calling party to the primary destination if the primary destination is determined to be free. 
     
     
       6. The method of claim 1, further comprising the step of establishing a voice path from the calling party to the primary destination if the primary destination is determined to be free. 
     
     
       7. The method of claim 1, wherein the secondary destination is comprised of a plurality of alternate destinations. 
     
     
       8. The method of claim 1 further comprising the step of: providing an audible indication to the calling party that the call is being processed if the local switch does not provide either the busy or the free indication associated with the primary destination.   
     
     
       9. The method of claim 8, wherein the audible indication is audible ringing. 
     
     
       10. A system for redirecting a telephone call from a busy primary destination to a secondary destination of a switched egress alternative destination redirection (ADR) customer when either a busy or free indication is not provided, comprising: a caller unit for placing a call to the switched egress ADR customer;   a first local switch for providing signalling information for routing the call to an originating switch, wherein said originating switch determines the primary destination and the secondary destination subscribed to by the ADR customer and provides signalling information for routing the call to a subscribed destination; and,   a second local switch for routing the call from the originating switch to a subscribed destination,   said originating switch further comprising a timer for timing a predetermined interval, wherein said timer is started if the second local switch does not provide the originating switch with signalling information that includes either the busy or the free indication associated with the primary destination when routing of the call to the primary destination is attempted, and   wherein said originating switch provides signalling information to the second local switch for redirecting the call to the secondary destination if the timer times the predetermined interval before the call is disconnected or before the call is answered at the primary destination.   
     
     
       11. The system of claim 10, wherein the secondary destination is comprised of a plurality of alternate destinations. 
     
     
       12. The apparatus of claim 10, wherein the originating switch provides an audible indication to the caller unit that the call is being processed if the second local switch does not provide the originating switch with signalling information that includes either the busy or the free indication associated with the primary destination when routing of the call to the primary destination is attempted. 
     
     
       13. The apparatus of claim 12, wherein the audible indication is audible ringing. 
     
     
       14. A system for redirecting a telephone call from a busy primary destination to a secondary destination of a switched egress alternative destination redirection (ADR) customer when either a busy or free indication is not provided, comprising: a caller unit for placing a call to the switched egress ADR customer;   a first local switch for providing signalling information for routing the call to an originating switch, wherein said originating switch determines the primary destination and the secondary destination subscribed to by the ADR customer and provides signalling information for routing the call to a subscribed destination;   a second local switch for routing the call from the originating switch to the subscribed primary destination; and,   a third local switch for routing the call from the originating switch to the subscribed secondary destination,   said originating switch further comprising a timer for timing a predetermined interval, wherein said timer is started if the second local switch does not provide the originating switch with signalling information that includes either the busy or the free indication associated with the primary destination when routing of the call to the primary destination is attempted, and   wherein said originating switch provides signalling information to the third local switch for redirecting the call to the secondary destination if the timer times the predetermined interval before the call is disconnected or before the call is not answered at the primary destination.   
     
     
       15. The system of claim 14, wherein the secondary destination is comprised of a plurality of alternate destinations. 
     
     
       16. The system of claim 14, wherein the originating switch provides an audible indication to the caller unit that the call is being processed if the second local switch does not provide the originating switch with signalling information that includes either the busy or the free indication associated with the primary destination when routing of the call to the primary destination is attempted. 
     
     
       17. The system of claim 16, wherein the audible indication is audible ringing. 
     
     
       18. A system for redirecting a telephone call from a busy primary destination to a secondary destination of a switched egress alternative destination redirection (ADR) customer when either a busy or free indication is not provided, comprising: a calling means for placing a call to the switched egress ADR customer;   a first switching means for providing signalling information for routing the call to a second switching means, wherein the second switching means determines the primary and the secondary destinations subscribed to by the ADR customer and provides signalling information for routing the call to a subscribed destination; and,   a third switching means for routing the call from the originating office to a subscribed destination,   said second switching means further comprising a timing means for timing a predetermined interval, wherein said timing means is started if the third switching means does not provide the second switching means with signalling information that includes either the busy or the free indication associated with the primary destination when routing of the call to the primary destination is attempted, and   wherein said second switching means provides signalling information to the third switching means for redirecting the call to the secondary destination if the timer times the predetermined interval before the call is disconnected or before the call is answered at the primary destination.   
     
     
       19. The system of claim 18, wherein the secondary destination is comprised of a plurality of alternate destinations. 
     
     
       20. The system of claim 18, wherein the second switching means provides an audible indication to the calling means that the call is being processed if the third switching means does not provide the second switching means with signalling information that includes either the busy or the free indication associated with the primary destination when routing of the call to the primary destination is attempted. 
     
     
       21. The system of claim 20, wherein the audible indication is audible ringing. 
     
     
       22. An apparatus comprising: a signalling information detector for detecting signalling information provided in a switching network;   a signalling information transmitter for providing signalling information for switching calls in the network;   a memory for storing data associated with switching calls in the network;   a timer for timing out predetermined intervals; and,   a processor,   wherein the processor accesses the memory for determining a primary and a secondary destination subscribed to by an ADR customer when a call is placed to the ADR customer,   wherein the processor provides control signals to the transmitter directing the transmitter to provide signalling information to a local switch for routing the call to the primary destination,   wherein the processor provides control signals to the timer directing the timer to time a predetermined interval if the local switch does not provide to the transmitter either a busy or free indication associated with the primary destination, and   wherein the processor provides control signals to the transmitter for redirecting the call to the secondary destination if the timer times out the predetermined interval before the call is disconnected or before the call is answered at the primary destination.   
     
     
       23. The apparatus of claim 22, wherein the processor provides signalling information to the transmitter directing the transmitter to establish a voice path from the calling party to the primary destination if the primary destination is determined to be free. 
     
     
       24. The apparatus of claim 22, wherein the secondary destination is comprised of a plurality of alternate destinations. 
     
     
       25. The apparatus of claim 22 further comprising: an announcer for playing an audible indication, wherein the processor provides control signals to the announcer directing the announcer to play the audible indication to the calling party that the call is being processed if the local switch does not provide to the transmitter either the busy or the free indication associated with the primary destination.   
     
     
       26. The apparatus of claim 25, wherein the audible indication is audible ringing.